Lawn full of worm casts - please help!!

As some of you will know, I had my back garden completely re-landscaped last year, including a lovely new lawn, so was gutted to find it full of worm casts this spring

. It has had one mowing 3 weeks ago, but now badly needs doing again. The trouble is, we've had so much rain over the past ten days that the mud doesn't dry off sufficiently to be raked off. The rest of this week is supposed to be dry, so I would really value some advice on how to deal with this problem. I'll attach a pic to show you a typical little pile, but this is repeated time and time again.

There was something about this on Garden Mania (or something like that) on BBC radio Newcastle recently - i think its still on I player - they were talking about some organic solution you can spay on your lawn that has some sulphur in it or something that the worms don't like. thats also supposed to make them go deeper and get rid of the casts.

Went into the GC today looking for a besom broom, and they'd actually got some in the Sale. So I got a Joseph Bentley one for £3.75 - lucky me! So I shall attack the worm casts tomorrow. Do you think the besom will work better if I trim all the birch twigs to roughly the same length?

Didn't have much joy with the besom, partly because by now the grass was above the casts, and also because even though the tops of the muddy piles were dry, the bottoms weren't. The broom just glided over the tops without moving them in the slightest!. So with a little old kitchen knife I have begun to dig out the solid stuff (which has now been flattened by the lawnmower), flicking it onto the top of the grass. When it dries it is much easier to sweep onto the patio with the besom. But it's going to take a long, long time - which I haven't got at the moment.